A virtual machine is a simulation of a computer system running within another host computer system. The virtual machine can be running the same operating system as the host computer system, or it can be running a different operating system. The virtual machine can include one or more virtual disks for data storage. One advantage of using a virtual machine is that the entire virtual machine system, along with its virtual disks, can be copied to a backup storage for preservation. The virtual machine system can then easily be restored to an earlier state in the case of data loss or system corruption. Some virtual machine backup systems create a single large backup file for the virtual machine and all of its associated data storage. However, some backup systems are able to separate the backup information for the virtual machine itself from the backup information for each of the virtual disks associated with the virtual machine. When a virtual machine backup is created in this way, backup recovery can be considerably more flexible. Backup recovery software can access the virtual disks directly to retrieve one or more files or directories, rather than rebuilding the entire backed up virtual machine and accessing the backup data through it. However, correlating backed up virtual disks to mounted disks on a running virtual machine is difficult, as volume mounting information is assigned arbitrarily when the machine is started up. The backup software is therefore prevented from being able to store a file retrieved from a backed up virtual disk in the correct location on the corresponding running virtual machine.